Adenosine is a well-known effector of immune function. In T-cells, adenosine decreases T-cell receptor induced activation of NF-κB, and inhibits IL-2, IL-4, and IFN-γ. Adenosine decreases T-cell cytotoxicity, increases T-cell anergy, and increases T-cell differentiation to Fop3+ or Lag-3+ regulatory (T-reg) T-cells. On NK cells, adenosine is known to decrease IFN-γ production, and suppress NK cell cytoxicity. Adenosine is known to block neutrophil adhesion and extravasation, decrease phagocytosis, and attenuate levels of superoxide and nitric oxide. Adenosine also decreases the expression of TNF-α, IL-12, and MIP-1α on macrophages, attenuates MHC Class II expression, and increases levels of IL-10 and IL-6. In addition, adenosine decreases phagocytosis and superoxide and nitric oxide levels on macrophages. Through these immune-related activities, and others, aberrant or accumulated levels of adenosine is associated with a number of diseases and conditions, including those in which the adenosine-mediated immunosuppressive effects play a role. Hence, there is a need for treatments of such diseases and conditions.